Activity
Tactile Model of Mendelian Trait in Pea Plants
Hands-on activity with a tactile model to teach students who are blind or visually impaired about the Medelian Trait in pea plants.
Mendel’s work with pea plants in the mid 1800s, earned him the title “The Father of Modern Genetics”. His work is discussed in most textbooks as an introduction to genetics as his hypotheses on heredity are still accepted. He observed 7 traits in pea plants including flower color, seed color, seed shape, pod color, pod shape, flower position, and plant height. This activity provides an accessible tactile model of seed shape using beads for activities in which Mendel’s work is modeled.
Purpose:
What did Mendel prove in his experiments with pea plants? In this investigation, you will model the genetic crosses that resulted in Mendel’s F2 generation.
Materials
- 1 pack of round smooth clear or white beads
- 1 pack of round faceted clear or white beads (“wrinkly” bead)
- small dixie cups
Note: It may be necessary to buy a pack of multicolored beads.
Preparation
- Place one round and 1 faceted bead in each Dixie cup
- Prepare tables in braille and print for students to record their results.
Procedure
- You will need one partner for this investigation. Each partner should have one smooth bead and one wrinkled bead. The smooth bead represents a gene for round seeds in pea plants. The wrinkled bead represents a gene for wrinkled seeds in pea plants.
- Close your hand around the two beads and place your hand behind your back. Shake the beads. Your partner does the same thing.
- Without looking at the beads, each partner chooses a bead. Look at the beads.
- Choose a letter to represent seed shape in pea plants. Then record the results of the cross in the table. The bead that you choose will be recorded in the column labeled “My gene” and the gene your partner chooses in the column labeled “My Partner’s Gene”
- Repeat steps 1–4 nine more times, filling in the chart as you go.
- After you have recorded the results of ten crosses, write the genotype and phenotype of each offspring in the table.
Questions and Conclusions
- What is the genotype and phenotype of the parents in the crosses you did?
- Draw a Punnett square to represent this cross.
What are the chances that the offspring will have round seeds?
Explore Further
Do the results of your investigation confirm the information on the Punnett square? Explain why or why not.
Variations
- This activity was originally designed for use with colored beads (purple and white) to represent the pea plant flower color variations.
- Students with low vision who have color vision could complete this activity utilizing colored beads if tactile sensitivity is difficult.
- This activity could be adapted to model the cross between P generation plants to show students why all of the F1 generation plants are heterozygous for the trait of seed shape.
NGSS Standards
Middle School – Growth, Development, and Reproduction of organisms
Variations of inherited traits between parent and offspring arise from genetic differences that result from the subset of chromosomes (and therefore genes) inherited. (MS-LS3-2)
Middle School – LS3.B: Variation of Traits
In sexually reproducing organisms, each parent contributes half of the genes acquired (at random) by the offspring. Individuals have two of each chromosome and hence two alleles of each gene, one acquired from each parent. These versions may be identical or may differ from each other.
By Laura Hospitál
This activity is adapted from the AGS Biology book by Charles J. LaRue, Ph.D. published in 2004
Pictures by Ditmar Hospitál
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